如何将数字的倍数推入数组？

Question

How would one push multiples of a number to an array? For example, if the input is (6), I want to create an array that holds [6, 12, 18, 24, 30, 36, etc...]

The most intuitive method to me does not work.

for (var i = 0; i < 10; i++) {
    firstArray.push(arr[0] *= 2);
}

This multiplies the number that comes before it by 2, causing an exponential growth. [14, 28, 56, 112, 224, 448, 896, 1792, etc.]

How would one achieve this?

Answer 1

Problem:

The problem in the code, as commented by Pranav is the use of multiplication by two in the for loop.

Using i iterator index can solve the problem.

firstArray.push(6 * (i + 1));

As i is starting from 0 , i + 1 will give the number which is 1-based .

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Another Approach:

First add the number

var num = 6,
    arr = [num];

Then add the number which is double of the previous in the array.

for (var i = 1; i < 10; i++) {
    arr.push(arr[i - 1] + num);
}

 var arr = [6]; for (var i = 1; i < 10; i++) { arr.push(arr[i - 1] + arr[0]); } console.log(arr); 

---

The same thing can also be done in single line using for loop.

 var arr = []; for (let i = 0, num = 6; i < 10; i++, num += 6) { arr.push(num); } console.log(arr); 

Answer 2

You can use map :

function multiplyArrayElement(num) {
    return num * 2;
}
numbers = [6, 12, 18, 24, 30, 36];

newArray = numbers.map(multiplyArrayElement);

https://jsfiddle.net/25c4ff6y/

Answer 3

It's cleaner to use Array.from . Just beware of its browser support.

Array.from({length: 10},(v,i) => (i + 1) * 6)

Answer 4

try this one

for (var i = 0; i < 10; i++) {
  firstArray.push(arr[0] * (i+1));
}

Answer 5

var arr = [];
var x = 6;   //Your desired input number
var z; 
for(var i=1;i<10;i++){
    z = (x*i);
    arr.push(z);
}
console.log(arr);

Answer 6

"One line" solution with Array.fill and Array.map functions:

var num = 6;

var arr = new Array(10).fill(0).map(function(v, k){ return num *(k + 1); });

console.log(arr); // [6, 12, 18, 24, 30, 36, 42, 48, 54, 60]